Integration of Design Modeling Techniques: Operations Automation Systems Scenario

This paper presents an application scenario in which knowledge-based and object oriented modeling techniques are applied and used in the analysis and design of complex, computer-based systems. The methodology is presented in the context of an operations automation and information management system in the electric utility operations problem domain. This system is referred to as OAS, for Operations Automation System in the remainder of this paper. The analysis and design methodology utilizes several techniques to analyze different aspects of the system in relative isolation. System Entity Specijkations (SE8 are used to decompose the system and to classih its components. The SES also serves as an anchor for linking the other models for traceability purposes, Use Case scenarios are used to model the system requirements. Object Modeling methods provide a rich mechanism for specihing the attributes and behavior of the system components. Dynamic modeling techniques, presented through the use of interaction diagrams, are used to model the dynamic behavior of system components and assist in the detailed system specijkation. The system presented in this paper is treated at a high level. The methodology supports iterative design and development so that the high-level design can be repeatedly re$ned, prototyped and tested until a suitably detailed design is produced. Introduction and Background The electric operations control room is an office, typically manned 24 hours a day by at least one electric system operator. The operator’s hdamental job is to ensure that customers are supplied with electric power 24 hours a day, 365 days a year with minimal interruptions. Customers expect to be able to consume power at any Jerzy W. Rozenblit Dept. of Computer and Electrical Engineering The University of Arizona Tucson, Arizona 85721, USA jmece. arizona. edu time they wish, in any quantity, limited only by the capacity of the equipment and protective devices serving their residence or commercial location. The power quality (voltage and frequency characteristic) is expected to be high at all times. A major component of the operator’s job is the management and direction of field crews in a variety of system activities. These activities include the installation of field equipment, routine maintenance of feeder equipment, and emergency restoration of power. The safety of field crews is the chief concem in this type of activity. For this reason, elaborate procedures, (typically paper and pencil based), have been developed to ensure equipment is in the proper state before construction, maintenance or reenergization activities are executed. The physical electrical system for most utilities is quite large. Major utilities organize their service territory into divisions. Divisions are often further subdivided into districts. The typical district contains between 20 and 100 distribution substations. Each substation provides power to between three and eight feeder circuits. The each fekder circuit delivers power to as many as 1500 of the utility’s customers. While there is usually one control room per district for daytime operation, it is common for a utility to consolidate operations and control into a single office responsible for providing “after hours” service for several districts. Control authority can be redistributed at any time if there is a storm or other event that requires more operators. The following list summarizes the typical tasks required of the electric system operators [ 11 : 0 Know the current state of the system and have a good understanding of what states may occur based on system load, weather, date and time. 0 Keep system voltage and loading within limits. 0 Monitor total system load, and in some cases shed load if it exceeds limits (for economic or system 158 0-8186-7355-9/96 $05.00